Acrylic synthetic fiber improved in styleability

ABSTRACT

An object of the present invention is to provide an acrylic synthetic fiber having excellent stylability and heat resistance. The object may be attained by an acrylic synthetic fiber having a knot-like unevenness on a fiber surface thereof, a difference of distances between a depression and a projection of 5.0 micrometers to 15.0 micrometers, a distance between peaks of unevenness of 0.05 mm to 0.5 mm, a flexural rigidity value of the fiber of 7.0×10 −7  N-m 2 /m to 10.0×10 −7  N-m 2 /m, and a torsional rigidity value of the fiber of 5.0×10 −9  N-m 2  to 10.0×10 −9  N-m 2 , and furthermore the object may be attained by an acrylic synthetic fiber comprising an acrylic copolymer having a content of acrylonitrile of not less than 60 mol %, a sulfur content originating in a vinyl based monomer including a sulfonic group of 0.15% by weight to 0.50% by weight, and a specific viscosity of 0.20 to 0.50.

This is a 371 national phase application of PCT/JP2003/008942 filled 14Jul. 2003, claiming priority to Japanese Application No. 2002-225317filed 1 Aug. 2002, the contents of which are incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to a fiber for artificial hair used forwigs, hairpieces, extension hairs (weavings), hair for dolls, etc., andto a fiber for hair having excellent stylability and heat resistance.

BACKGROUND ART

In general, a large number of fibers, such as, acrylic fibers, vinylchloride based fibers, and polyamide fibers, or polyester fibers aremarketed as artificial fibers for hair. However, since these fibers arenot simultaneously provided with all characteristics necessary as anartificial fiber for hair, such as heat resistance, curling property,and touch, each material has limited advantageous style fields for wigs.For example, conventional fibers are classified into synthetic fiberssuitable for curly style, or synthetic fibers suitable for straightstyle, respectively, and since only a few synthetic fibers having widestylability (fiber function enabling various styles for wigs) aremarketed, development of such synthetic fibers are now demanded. Forthis reason, in order to improve stylability, for example, JapanesePatent Laid-Open No. 55-158322 official report, Japanese PatentLaid-Open No. 56-63006 official report, and Japanese Patent Laid-OpenNo. 58-4809 official report disclose techniques for accomplishingobjects thereof by giving specific unevenness to a fiber surface.Although application of specific unevenness to a fiber surface iseffective method for improvement in stylability, indeed, onlyapplication of simple surface unevenness cannot improve rigidity of thefiber, and, as a result, cannot sufficiently satisfy salability ofstraight style. Low heat resistance thereof does not allow use ofthermal instruments, such as hair driers, and does not easily enablecreation of hair style suitable for taste of each individual, andtherefore many users require improvement in the point.

SUMMARY OF THE INVENTION

The present invention relates to providing a fiber bundle for artificialhair, for solving the problems, and for use of wigs, hairpieces,extension hairs (weaving), hair for dolls, etc. by an acrylic syntheticfiber having a knot-like unevenness on a fiber surface thereof, andhaving flexural rigidity and torsional rigidity values within a specificrange. Moreover, the present invention relates to providing a fiber forartificial hair having excellent stylability and heat resistance.

The present inventors found out that application of a knot-likeunevenness onto a fiber surface of an acrylic synthetic fiber comprisingan acrylic copolymer, and limitation of flexural rigidity and torsionalrigidity of the fiber within a specific range could solve the problem.

That is, the present invention relates to an acrylic synthetic fiberhaving a knot-like unevenness on a fiber surface thereof, a differenceof distances between a depression and a projection of 5.0 micrometers to15.0 micrometers, a distance between peaks of unevenness of 0.05 mm to0.5 mm, a flexural rigidity value of the fiber of 7.0×10⁻⁷ N-m²/m to10.0×10⁻⁷ N-m²/m, and a torsional rigidity value of the fiber of5.0×10⁻⁹ N-m² to 10.0×10⁻⁹ N-m².

Preferably the fiber is an acrylic synthetic fiber comprising an acryliccopolymer having a content of acrylonitrile of not less than 60 mol %, asulfur content originating in a vinyl based monomer including a sulfonicgroup of 0.15% by weight to 0.50% by weight, and a specific viscosity of0.20 to 0.50 in the acrylic copolymer.

It is preferable that 10% shrinkage starting temperature of the acrylicsynthetic fiber is not less than 150 degrees C.

It is preferable that an artificial hair consists of the acrylicsynthetic fiber.

The present invention will, hereinafter, be described in detail. Thepresent invention relates to an acrylic synthetic fiber having aknot-like unevenness on a fiber surface thereof, a difference ofdistances between a depression and a projection of 5.0 micrometers to15.0 micrometers, a distance between peaks of unevenness of 0.05 mm to0.5 mm, a flexural rigidity value of the fiber of 7.0×10⁻⁷ to 10.0×10⁻⁷N-m²/m, and a torsional rigidity value of 5.0×10⁻⁹ to 10.0×10⁻⁹ N-m².

Acrylic synthetic fiber as used in the present invention has a knot-likeunevenness and a difference of distances between a depression and aprojection of 5.0 micrometers to 15.0 micrometers (difference ofdepressed area of fiber surface and projected area) on a fiber surface,and preferably 6.0 micrometers to 12.0 micrometers, as shown in FIG. 1.Moreover, it has a distance between peaks of unevenness of 0.05 mm to0.5 mm (distance of a projected area on surface of fiber, and aneighboring projected area), and preferably 0.06 mm to 0.40 mm. Adifference of distances between a depression and a projection of lessthan 5.0 micrometer cannot give intended stylability, and a differenceexceeding 15.0 micrometers gives severe frictional property onto asurface of the fiber, resulting in occurrence of troubles, such as yarnbreakage in a processing process of wigs. Moreover, a distance betweenpeaks of unevenness of less than 0.05 mm gives severe frictionalproperty on a surface of the fiber, and occurs troubles, such as yarnbreakage in a processing process of wigs, and a difference exceeding 0.5mm cannot give intended stylability. An acrylic synthetic fiber of thepresent invention has a flexural rigidity value of 7.0×10⁻⁷ to 10.0×10⁻⁷N-m²/m, preferably 7.0×10⁻⁷ to 9.0×10⁻⁷ N-m²/m, and more preferably7.5×10⁻⁷ to 8.5×10⁻⁷ N-m²/m. A flexural rigidity value of less than7.0×10⁻⁷ N-m²/m gives weak flexural rigidity, and insufficientstylability to the fiber, and a flexural rigidity exceeding 10.0×10⁻⁷N-m²/m hardens touch of the fiber, and makes the fiber unsuitable as anartificial hair.

Moreover, an acrylic synthetic fiber of the present invention has atorsional rigidity value of not more than 5.0×10⁻⁹ to 10.0×10⁻⁹ N-m²,preferably 5.0×10⁻⁹ to 9.6×10⁻⁹ N-m², and more preferably 5.0×10⁻⁹ to9.3×10⁻⁹ N-m². A torsional rigidity value less than 5.0×10⁻⁹ N-m²weakens torsional rigidity of the fiber, and gives insufficientstylability, and a torsional rigidity value exceeding 10.0×10⁻⁹ N-m²hardens touch of the fiber, making the fiber unsuitable as an artificialhair.

In measurement of the flexural rigidity and torsional rigidity of afiber as used in the present invention, a bending moment is measuredbased on a repulsive force in each curvature of an acrylic syntheticfiber being bent using a flexural rigidity measurement machine(KES-FB2-S, made by Kato Tech Co., Ltd.), as described later. Moreover,in measurement of the torsional rigidity, using a torsional rigiditymeasurement machine (KES-YN1, made by Kato Tech Co., Ltd.), a torsionalmoment is measured based on a repulsive force of a rotated acrylicsynthetic fiber.

A content of acrylonitrile in an acrylic copolymer constituting anacrylic synthetic fiber of the present invention is preferably not lessthan 60 mol %, and more preferably not less than 65 mol %. An upperlimit is preferably 90 mol %, and more preferably 85 mol %. There isshown a tendency for a content of acrylonitrile of less than 60 mol % tomake insufficient heat resistance of the acrylic synthetic fiber.Moreover, there is shown a tendency for a content of acrylonitrileexceeding 90 mol % to impair touch and flame resistance that is anadvantageous feature of an acrylic synthetic fiber. Heat resistancerequired by the present invention means durability of an acrylicsynthetic fiber over heat of a drier, and in this point, the acrylicsynthetic fiber preferably has a 10% shrinkage starting temperature ofnot less than 150 degrees C., and more preferably not less than 155degrees C. A 10% shrinkage starting temperature of less than 150 degreesC. induces curl and welding by shrinkage of a fiber, and there is showna tendency of reduction of commodity value. Moreover, an upper limitvalue of 10% shrinkage starting temperature is preferably 180 degrees C.Although the temperature exceeding 180 degrees C. improves heatresistance, there is shown a tendency for curl-set hard to be given.Here, a 10% shrinkage starting temperature means a temperature obtainedby a following method. First, a fiber bundle is heat-treated underconditions of arbitrary temperature and unstrained for 30 minutes, and asample length LD (mm) after cooling to a room temperature is measured. Adry heating shrinkage percentage to the sample length before heattreatment L (mm) is determined by a following equation. Next,extrapolation is performed in relation to each temperature and dryheating shrinkage percentage to obtain a 10% shrinkage startingtemperature (T10).Dry heating shrinkage percentage (%)=[L (20.0 cm)−LD]/L (20.0 cm)]×100

Moreover, an acrylic copolymer constituting an acrylic synthetic fiberof the present invention uses a vinyl monomer including a sulfonic groupas a copolymerizable component. Preferably, the percentage to be used isset so that a sulfur content originating in a vinyl based monomerincluding a sulfonic group in the acrylic copolymer may be 0.15% byweight to 0.50% by weight, and more preferably 0.20% by weight to 0.40%by weight. A sulfur content less than 0.15% by weight of originating invinyl based monomer including a sulfonic group is prone to makedifficult development of pores in a fiber necessary for applyingunevenness to a surface of the fiber, and to reduce dye affinity, asdescribed later. And the sulfur content exceeding 0.50% by weight maynot improve effects of the present invention, and causes costdisadvantage.

Moreover, a specific viscosity of an acrylic copolymer is a factor thatcontrols flexural rigidity and torsional rigidity of the fiber. Thespecific viscosity concerned is preferably 0.20 to 0.50, more preferably0.22 to 0.45, and still more preferably 0.25 to 0.40. A specificviscosity less than 0.20 reduces flexural rigidity and torsionalrigidity, and shows a tendency for desired stylability not to be given.A specific viscosity exceeding 0.50 excessively raises a viscosity of aspinning solution obtained by dissolving the acrylic copolymer in asolvent, and disadvantageously shows a tendency of poor productivity.

Here, the specific viscosity as used herein is obtained by measuring apolymer solution of (an acrylic copolymer 2 g/dimethylformamide 1 L) fora viscosity at 30 degrees C. with an Ostwald type viscometer.

Hereinafter, descriptions will be given about general method formanufacturing an acrylic synthetic fiber of the present invention.

As methods, and devices, etc. for manufacturing an acrylic copolymerused in order to manufacture an acrylic synthetic fiber, generalwell-known polymerization methods and after-treatment methods may beused.

As copolymerizable components for acrylonitrile, vinyl monomersincluding halogen, mono-olefine based monomers, etc. may be mentioned,and when a content of the acrylonitrile in the acrylic copolymer is notless than 60 mol %, well-known vinyl monomers may be used. The vinylmonomers including halogen are especially effective as a component forgiving flame resistance to the acrylic copolymer as a fiber. Such vinylmonomers including halogen are not especially limited, as long as theyare copolymerizable with acrylonitrile. As the vinyl monomers includinghalogen, for example, but not limited to, vinylidene chloride, vinylchloride, vinylidene bromide, vinyl bromide, etc. may be mentioned.Vinylidene chloride and vinyl chloride are preferable in respect of easyavailability among them. Moreover, other mono-olefine based monomerscopolymerizable with them may be used in a level not adversely affectingthe present invention. As other mono-olefin monomers, for example, butnot limited to, acrylic acid, methacrylic acid and esters thereof,acrylamide, vinyl acetate, etc. may be mentioned. Methyl acrylate andmethyl methacrylate are preferable in respect of excellent reactivityand improvement in dye affinity among them.

Moreover, as vinyl based monomer including a sulfonic group, there maybe mentioned, for example, but not limited to, sodiumpara-styrenesulfonate, sodium methallylsulfonate, sodium isoprenesulfonate(2-methyl-1,3-butadiene-1-sodium sulfonate),2-acrylamido-2-sodium methyl propane sulfonate(acrylamide-t-butyl-sodiumsulfonate), para-styrene sulfonic acid, methallyl sulfonic acid,isoprene sulfonic acid (2-methyl-1,3-butadiene-1-sulfonic acid),2-acrylamido-2-methyl propane sulfonic acid (acrylamide-t-butyl-sulfonicacid) etc. From points of the easy availability, and excellentreactivity among them, sodium para-styrenesulfonate, sodium isoprenesulfonate or sodium methallylsulfonate, 2-acrylamido-2-methyl propanesulfonic acid (acrylamide-t-butyl-sulfonic acid) are preferable.

Following methods may be mentioned as preferable methods for developinga knot-like unevenness on a surface of the acrylic synthetic fiber. Incase of using an acrylic copolymer soluble in acetone, an acryliccopolymer having a content of acrylonitrile of not less than 60 mol % isdissolved in acetone as a solvent to obtain a a spinning solution having20% to 35% by weight, preferably 25% to 32% by weight of resinconcentration. A value of viscosity (for 12 rpm and 30 seconds) of thespinning solution measured with a Brookfield viscometer manufactured byTOKIMEC is preferably not less than 40 poise at 40 degrees C. to 50degrees C., and more preferably 50 poise to 70 poise. A manufacturingprocess is performed by wet spinning method using the spinning solution.In a range of not adversely affecting the present invention, otheradditives, such as ultraviolet absorbers, may be used in the spinningsolution.

A hole shape of a nozzle used herein may have a round shape, a dumbbelltype, or a ★ shape, but it is not especially limited to them. A nozzledraft (a nozzle draft designates a ratio of extruding velocity of aspinning solution from the nozzle hole and a taking up velocity) is afactor that controls a difference of distances between a depression anda projection and a distance between peaks of unevenness on a surface ofthe acrylic synthetic fiber. For example, a nozzle draft when using anon-circular nozzle having the above described ★ type is preferably atleast 0.7, and more preferably in a range of 0.80 to 1.3. A nozzle draftless than 0.7 disadvantageously makes smaller a difference of distancesbetween a depression and a projection on a surface of the resultingacrylic synthetic fiber obtained, and furthermore enlarges a distancebetween peaks of unevenness.

A coagulation bath is of an aqueous solution of acetone and ispreferably adjusted to 30% by weight to 50% by weight of acetoneconcentration, and 15 degrees C. to 30 degrees C. of a bath temperature,and more preferably 35% by weight to 40% by weight of acetoneconcentration, and 20 degrees C. to 25 degrees C. of a bath temperature.Spinning carried out under this condition can give pores to a crosssection of the acrylic synthetic fiber. Conditions out of the range ofthe coagulation bath cannot give pores to a cross section of the acrylicsynthetic fiber, and as a result, there is shown a tendency for surfaceunevenness obtained by pores collapsed by drying not to be formed. Theobtained yarn is washed with water, dried with wet heated wind at atemperature of not less than 100 degrees C. and a wet-bulb temperatureof not less than 60 degrees C., and lost transparency recovery treatmentis given. After the yarn is stretched, the yarn is heat treated toobtain an acrylic synthetic fiber. At this time, a treatment by 5% to30% of relaxation percentage can reduce a heat shrinkage rate thereof.When a relaxation percentage is out of the range, there is shown anunpreferable tendency for quality as a fiber for artificial hair to bedeteriorated. Besides, a size of a fiber of the acrylic synthetic fiberof the present invention is preferably 25 decitexes to 75 decitexes, andmore preferably 40 decitexes to 60 decitexes. There is shown a tendencyfor a size of a fiber of the acrylic synthetic fiber less than 25decitexes to weaken retentivity of curl, and a size of a fiber exceeding75 decitexes to increase rigidity, impairing stylability as anartificial hair. As a cross section shape of the acrylic syntheticfiber, a horseshoe type, a dumbbell type, a round shape, etc. arepreferable, but it is not limited to them.

In case of using an acrylic copolymer having a high content ofacrylonitrile, a target fiber may be obtained by methods shownhereinafter. The acrylic copolymer is dissolved in solvents, such asdimethylformamide (DMF) and dimethylacetamide (DMAc) to obtain aspinning solution concentration of 20% to 35% by weight. The spinningsolution is extruded into a coagulation bath including an aqueoussolution of a solvent such as DMF and DMAc, having a bath temperatureadjusted at 15 degrees C. to 35 degrees C. and a concentration of DMF orDMAc adjusted to 30% by weight to 90% by weight, with a nozzle draft of0.5 to 1.2, using a round shape or a non-circular nozzle with ★ shape.Then the yarn extruded is processed by well-known methods. Here, anacrylic copolymer having a high content of acrylonitrile designates anacrylic copolymer having a content of acrylonitrile of 70 mol % to 90mol % in the acrylic copolymer.

The acrylic synthetic fiber obtained in the above-described methods isused for headdress products, such as wigs, hairpieces, extension hairs(weavings), and hair for dolls, using well-known methods.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photograph showing a surface unevenness of an acrylicsynthetic fiber in Example 1;

FIG. 2 is a photograph showing a surface unevenness of an acrylicsynthetic fiber in Comparative Example 1; and

FIG. 3 is a photograph showing a surface of an acrylic synthetic fiberin Comparative Example 3.

BEST MODE FOR CARRYING-OUT OF THE INVENTION

Although descriptions will, hereinafter, be given in more detail withreference to Examples, the present invention is not limited to theExamples. Besides, descriptions about definitions of measuring methodsetc. will be given in advance of Examples. (Method for measuring asulfur content originating in a vinyl based monomer including a sulfonicgroup)

Measurement of a sulfur content originating in vinyl monomer including asulfonic group was carried out using a following method. A resin of anacrylic copolymer 0.1 g was burned under conditions of an atmosphere ofargon/oxygen=100/100, a heating temperature of 900 degrees C., and aheating period of time 35 minutes to obtain a combustion gas, using asample combustion apparatus (QF-02, made by Mitsubishi ChemicalCorporation). The gas was absorbed in 0.3% by weight of hydrogenperoxide aqueous solution to obtain sulfate ion. The sulfate ion wasanalyzed using an ion chromatography (IC-7000, made by YokogawaAnalytical Systems Inc.), and then a sulfur content was calculated froma content of the sulfate ion. Next, a sulfur content originating in anpolymerization initiator is deducted from the obtained value, and thus asulfur content of the vinyl based monomer including a sulfonic grouporigin was calculated. Besides, a sulfur content originating in thepolymerization initiator was calculated by a same method using anacrylic copolymer including no vinyl monomer including a sulfonic group.

(Method for Measuring a Resin Composition)

In the method, a nitrogen content in a resin was measured using a CHNCorder (made by Yanaco, Inc.), and then an acrylonitrile content wascalculated using the nitrogen content as a nitrogen content originatingin acrylonitrile.

(Method for Measuring a Specific Viscosity)

A specific viscisity was measured for a polymer solution of (acryliccopolymer 2 g)/(dimenthylformamide 1L) at 30 degrees C. using an Ostwaldtype viscometer.

(Method for Measuring a Viscosity of a Spinning Solution) A viscosity(for 12 rpm and 30 seconds) was measured at 40 degrees C. using aBrookfield viscometer (made by TOKIMEC Corp.)

(Method for Measuring a Surface Unevenness)

A fiber was observed for a difference of distances between a depressionand a projection and a distance between peaks of unevenness using anoptical microscope with 100 times of magnification, and calculation wasperformed.

(Method for Measuring a Flexural Rigidity)

In the method, using a flexural rigidity measuring machine (KES-FB2-S,manufactured by Kato Tech Co., Ltd.), measurement was performed for asample obtained by arranging 49 units of acrylic synthetic fibers with alength of 1 cm at intervals of 1 mm, under a condition of bendingcurvature of ±2.5 cm, and then an average value was calculated for 3times of measurements to obtain a flexural rigidity value (unit:N-m²/m).

(Method for Measuring a Torsional Rigidity)

A sample with a length of 2 cm was measured for a torsional rigidityunder conditions of a twist number of rotations of ±3 revolutions, and atwist speed of 12 degree/second, using a torsional rigidity measurementmachine (KES-YN1, made by Kato Tech Co., Ltd.), and then an averagevalue was calculated for 10 times of measurements to obtain a torsionalrigidity (unit: N-m²)

(Method Measuring a Dry Heating Shrinkage Percentage)

A fiber bundle was heat-treated under conditions of arbitrarytemperature and unstrained for 30 minutes, and then a sample length LD(mm) after cooling to a room temperature was measured. A dry heatingshrinkage percentage might be obtained for shrinkage percentage of thesample length LD (mm) to a sample length L (mm) before heat treatment bya following equation. Moreover, from a relationship between temperaturesand dry heating shrinkage percentages, a 10% shrinkage startingtemperature was calculated by extrapolation, and defined as T10.Dry heating shrinkage percentage (%)=[L (20.0 cm)−LD]/L(20.0 cm)]×100(Method for Evaluating Stylability)

A pageboy style was formed, and the style was evaluated for retentivityof curl, stability of curl, bulkiness, and set of a surface by fivecommon engineers engaged in cosmetics evaluation of wigs etc. Five-gradeevaluation was performed in each item, and when a style has not lessthan 4 grade in all items, the style was evaluated as acceptable.

Criterion for Evaluation

-   5: Excellent-   4: Good-   3: Moderate-   2: Poor-   1: Very poor    (Method for Evaluating Blow Property)

In the method for evaluating blow property (heat resistance), fivecommon engineers engaged in cosmetics evaluation of wigs etc. evaluateda sample for points of curling of hair ends and welding, using acommercially available hair drier (120 degrees C. to 140 degrees C.), ina same manner as in the method for evaluating stylability. Theevaluations were integrated, five-grade evaluation shown hereinafter wasperformed, and a point of not less than 4 was considered to beacceptable.

-   5: Breakage on hair not observed at all-   4: Almost no breakages on hair observed-   3: Breakage on hair as a curl observed for a part of hair ends-   2: Breakage on hair as curl and welding of hair ends observed-   1: Heavy breakage on almost all hair ends of curl and welding    observed

EXAMPLE 1

An acrylic polymer resin comprising acrylonitrile 52% by weight, vinylchloride 4% by weight, vinylidene chloride 42.6% by weight, and sodiumstyrene sulfonate 1.4% by weight had a content of acrylonitrile of 66mol %, a sulfur content originating in vinyl based monomer including asulfonic group of 0.22% by weight, and a specific viscosity of 0.26. Theresin was dissolved in acetone to obtain a spinning solution prepared soas to have a resin concentration of 26.0% by weight. The spinningsolution had a viscosity of 55 poises. Using a nozzle with anon-circular cross section having a shape of “∈” (0.3 mm of pore size,25 numbers of holes) under a condition of nozzle draft of 0.90, thespinning solution was extruded in an aqueous solution having an acetoneconcentration of 36% by weight, and a temperature of 25 degrees C.

Moreover, a yarn extruded was led to a washing water bath at 50 degreesC. to 60 degrees C., stretched 1.93 times while being washed with water,and subsequently, was dried at a drying temperature of 125 degrees C.,and a wet-bulb temperature of 70 degrees C., to recover losttransparency. After hot-stretched by 2.0 times, the yarn was furthermoreheat treated at 160 degrees C. and relaxed by 8%. An acrylic syntheticfiber having a single yarn size of 51 decitexes was obtained.

Thus obtained acrylic synthetic fiber had a cross section shape ofalmost round shape, and had a knot-like unevenness on a surface thereof,a difference of distances between a depression and a projection of 7.0micrometers and a distance between peaks of unevenness of 0.25 mm.Moreover, the yarn had a flexural rigidity value of 7.5×10⁻⁷ N-m²/m, atorsional rigidity value of 5.0×10⁻⁹ N-m², and a 10% shrinkage startingtemperature (T10) of 156 degrees C. A pageboy style was formed using theacrylic synthetic fiber to perform evaluation. Table 1 shows results.FIG. 1 is a photograph showing a surface unevenness of an acrylicsynthetic fiber 1 in Example 1. The fiber has a a knot-like unevennesson a surface thereof. VC represents vinyl chloride in the Table 1, andVD represents vinylidene chloride.

EXAMPLE 2

An acrylic polymer resin comprising acrylonitrile 63% by weight,vinylidene chloride 35.5% by weight, and sodium styrene sulfonate 1.5%by weight had a content of acrylonitrile of 76 mol %, a sulfur contentoriginating in the vinyl based monomer including a sulfonic group of0.23% by weight, and a specific viscosity of 0.40. The resin wasdissolved in dimethylacetamide to obtain a spinning solution prepared soas to have a resin concentration of 20.0% by weight. The spinningsolution had a viscosity of 70 poises. Using a nozzle with a circularcross section (0.3 mm of pore size, 25 numbers of holes) under acondition of nozzle draft of 0.81, the spinning solution was extruded inan aqueous solution having a dimethylacetamide concentration of 60% byweight, and a temperature of 25 degrees C. Moreover, a yarn extruded wasled to a washing water bath at 50 degrees C. to 60 degrees C., stretched1.93 times while being washed with water, and subsequently, was dried ata drying temperature of 125 degrees C., and a wet-bulb temperature of 70degrees C., to recover lost transparency. After hot-stretched by 2.5times, the yarn was furthermore heat treated at 160 degrees C. andrelaxed by 8%. An acrylic synthetic fiber having a single yarn size of51 decitexes was obtained.

Thus obtained acrylic synthetic fiber had a cross section shape ofalmost round shape, and had a knot-like unevenness on a surface thereof,a difference of distances between a depression and a projection of 8.0micrometers and a distance between peaks of unevenness of 0.27 mm.Moreover, the yarn had a flexural rigidity value of 8.4×10⁻⁷ N-m²/m, atorsional rigidity value of 9.2×10⁻⁹ N-m², and a 10% shrinkage startingtemperature (T10) of 165 degrees C. Evaluation was performed in a samemanner as in Example 1 for the acrylic synthetic fiber. Table 1 showsresults.

Comparative Example 1

An acrylic polymer resin comprising acrylonitrile 48% by weight, vinylchloride 51% by weight, and sodium styrene sulfonate 1.0% by weight hada content of acrylonitrile of 53 mol %, a sulfur content originating invinyl based monomer including a sulfonic group of 0.16% by weight, and aspecific viscosity of 0.18. The resin was dissolved in acetone to obtaina spinning solution prepared so as to have a resin concentration of29.0% by weight. The spinning solution had a viscosity of 40 poises.Using a nozzle with a non-circular cross section having a shape of “∈”(0.3 mm of pore size, 25 numbers of holes) under a condition of nozzledraft of 0.80, the spinning solution was extruded in an aqueous solutionhaving an acetone concentration of 38% by weight, and a temperature of25 degrees C. Moreover, a yarn extruded was led to a washing water bathat 50 degrees C. to 60 degrees C., stretched 1.9 times while beingwashed with water, and subsequently, was dried at a drying temperatureof 125 degrees C., and a wet-bulb temperature of 70 degrees C., torecover lost transparency. After hot-stretched by 2.0 times, the yarnwas furthermore heat treated at 160 degrees C. and relaxed by 8%. Anacrylic synthetic fiber having a single yarn size of 53 decitexes wasobtained.

Thus obtained acrylic synthetic fiber had a cross section shape ofalmost round shape, and had a knot-like unevenness on a surface thereof,a difference of distances between a depression and a projection of 5.5micrometers and a distance between peaks of unevenness of 0.30 mm.Moreover, the yarn had a flexural rigidity value of 6.5×10⁻⁷ N-m²/m, atorsional rigidity value of 4.7×10⁻⁹ N-m², and a 10% shrinkage startingtemperature (T10) of 138 degrees C. Evaluation was performed in a samemanner as in Example 1 for the acrylic synthetic fiber. Table 1 showsresults. FIG. 2 is a photograph showing a surface unevenness of theacrylic synthetic fiber 2 in Comparative Example 1. The fiber had aknot-like unevenness on a surface thereof.

Comparative Example 2

An acrylic polymer resin comprising acrylonitrile 48% by weight, vinylchloride 51.5% by weight, and sodium styrene sulfonate 0.5% by weighthad a content of acrylonitrile of 53 mol %, a sulfur content originatingin vinyl based monomer including a sulfonic group of 0.078% by weight,and a specific viscosity of 0.17. The resin was dissolved in acetone toobtain a spinning solution prepared so as to have a resin concentrationof 28.0% by weight. The spinning solution had a viscosity of 45 poises.Using a nozzle with a circular cross section (0.3 mm of pore size, 25numbers of holes) under a condition of nozzle draft of 0.82, thespinning solution was extruded in an aqueous solution having an acetoneconcentration of 20% by weight, and a temperature of 25 degrees C.Moreover, a yarn extruded was led to a washing water bath at 50 degreesC. to 60 degrees C., stretched 1.9 times while being washed with water,and subsequently, was dried at a drying temperature of 125 degrees C.,and a wet-bulb temperature of 70 degrees C., to recover losttransparency. After hot-stretched by 2.0 times, the yarn was furthermoreheat treated at 160 degrees C. and relaxed by 8%. An acrylic syntheticfiber having a single yarn size of 53 decitexes was obtained.

Although the acrylic synthetic fiber thus obtained had a horseshoe shapecross-section, it did not have unevenness on a surface thereof.Moreover, the yarn had a flexural rigidity value of 6.5×10⁻⁷ N-m²/m, atorsional rigidity value of 4.5×10⁻⁹ N-m², and a 10% shrinkage startingtemperature (T10) of 138 degrees C. Evaluation was performed in a samemanner as in Example 1 for the acrylic synthetic fiber. Table 1 showsresults.

Comparative Example 3

An acrylic polymer resin comprising acrylonitrile 52% by weight, vinylchloride 4% by weight, vinylidene chloride 42.6% by weight and sodiumstyrene sulfonate 1.4% by weight had a content of acrylonitrile of 66mol %, a sulfur content originating in the vinyl based monomer includinga sulfonic group of 0.22% by weight, and a specific viscosity of 0.26.The resin was dissolved in acetone to obtain a spinning solutionprepared so as to have a resin concentration of 26.0% by weight. Thespinning solution had a viscosity of 55 poises. Using a nozzle with anon-circular cross section having a shape of∈(0.4 mm of pore size, 25numbers of holes) under a condition of nozzle draft of 1.30, thespinning solution was extruded in an aqueous solution having an acetoneconcentration of 25% by weight, and a temperature of 25 degrees C.Moreover, a yarn extruded was led to a washing water bath at 50 degreesC. to 60 degrees C., stretched 2.0 times while being washed with water,and subsequently, was dried at a drying temperature of 125 degrees C.,and a wet-bulb temperature of 70 degrees C., to recover losttransparency. After hot-stretched by 2.4 times, the yarn was furthermoreheat treated at 160 degrees C. and relaxed by 8%. An acrylic syntheticfiber having a single yarn size of 51 decitexes was obtained.

Although the acrylic synthetic fiber thus obtained had an almost roundshape, it did not have unevenness on a surface thereof. Moreover, theyarn had a flexural rigidity value of 7.5×10⁻⁷ N-m²/m, a torsionalrigidity value of 5.0×10⁻⁹ N-m², and a 10% shrinkage startingtemperature (T10) of 156 degrees C. Evaluation was performed in a samemanner as in Example 1 for the acrylic synthetic fiber. Table 1 showsresults. FIG. 3 is a photograph showing a surface unevenness of theacrylic synthetic fiber 3 in Comparative Example 3. Knot-like unevennesswas not observed on a surface of the fiber.

TABLE 1 Monomer content in polymer Vinyl monomer Sulfur contentoriginating Unevenness Acrylo- including in vinyl based monomer SpecificDifference Distance nitrile halogen wt % including a sulfonic group wt %viscosity micrometer mm Example 1 66 mol % VC4 0.22 0.26 7.0 0.25 (52 wt%) VD 42.6 Example 2 76 mol % VD 35.5 0.23 0.40 8.0 0.27 (63 wt %)Comparative Example 1 53 mol % VC 51.0 0.16 0.18 5.5 0.30 (48 wt %)Comparative Example 2 53 mol % VC 51.5 0.078 0.17 0 0 (48 wt %)Comparative Example 3 66 mol % VC4 0.22 0.26 0 0 (52 wt %) VD 42.6Rigidity Syllabicity Flexural × 10⁻⁷ Torsional × 10⁻⁹ Curl Curl Set ofBlow (N − m²/m) (N − m²) T₁₀ retentivity stability Bulkiness surfaceproperty Example 1 7.5 5.0 156 5 5 5 5 4 Example 2 8.4 9.2 165 4 5 4 5 5Comparative Example 1 6.5 4.7 138 4 4 2 5 3 Comparative Example 2 6.54.5 138 4 3 4 3 2 Comparative Example 3 7.5 5.0 156 5 3 5 5 4 (Note) wt% = % by weight, Mol % = mol %, Part = part by weightAs Table 1 shows clearly, Examples 1 and 2 have excellent stylabilityand excellent blow property (heat resistance).

INDUSTRIAL APPLICABILITY

The present invention provides an artificial hair comprising an acrylicsynthetic fiber having excellent stylability and heat resistance, theacrylic synthetic fiber having a knot-like unevenness on a fiber surfacethereof, a difference of distances between a depression and a projectionof 5.0 micrometers to 15.0 micrometers, a distance between peaks ofunevenness of 0.05 mm to 0.5 mm, a flexural rigidity value of the fiberof 7.0×10⁻⁷ N-m²/m to 10.0×10⁻⁷ N-m²/m, and a torsional rigidity valueof the fiber of 5.0×10⁻⁹ N-m² to 10.0×10⁻⁹ N-m².

1. An acrylic synthetic fiber having a knot-like unevenness on a fibersurface thereof, a difference of distances between a depression and aprojection of 5.0 micrometers to 15.0 micrometers, a distance betweenpeaks of unevenness of 0.05 mm to 0.5 mm, a flexural rigidity value ofthe fiber of 7.0×10⁻⁷ N-m²/m to 10.0×10⁻⁷ N-m²/m, and a torsionalrigidity value of the fiber of 5.0×10⁻⁹ N-m² to 10.0×10⁻⁹ N-m².
 2. Theacrylic synthetic fiber according to claim 1 comprising an acryliccopolymer having a content of acrylonitrile of not less than 60 mol %, asulfur content originating in a vinyl based monomer including a sulfonicgroup of 0.15% by weight to 0.50% by weight, and a specific viscosity of0.20 to 0.50.
 3. The acrylic synthetic fiber according to claim 1,wherein a 10% shrinkage starting temperature of the acrylic syntheticfiber is not less than 150 degrees C.
 4. An artificial hair comprisingthe acrylic synthetic fiber according to claim
 1. 5. The acrylicsynthetic fiber according to claim 2, wherein a 10% shrinkage startingtemperature of the acrylic synthetic fiber is not less than 150 degreesC.
 6. An artificial hair comprising the acrylic synthetic fiberaccording to claim
 2. 7. An artificial hair comprising the acrylicsynthetic fiber according to claim 3.